Vessels are commonly treated to reduce or eliminate narrowings caused by arteriosclerotic disease. Interventional treatments can include use of balloon angioplasty, stenting, thrombectomy, atherectomy, and other procedures. During treatment particulate debris can be generated at the treatment site. Infarcts, strokes, and other major or minor adverse events are caused when debris embolizes into vasculature from the treatment site.
To prevent embolization of debris, embolic protection devices have been developed. During a procedure such devices can be placed distal or proximal to the treatment site. Embolic protection devices can remove emboli from the bloodstream by filtering debris from blood, by occluding blood flow followed by aspiration of debris, or can cause blood flow reversal to effect removal of debris. The shape, length and other characteristics of an embolic protection device are typically chosen based on the anatomical characteristics in the vicinity of the treatment site. However, some anatomies present specific challenges due to the anatomical shape or configuration.
Difficulties can arise where embolic protection devices are not properly deployed within the anatomy. For example, if a device does not properly engage a lumenal wall, leaving a gap between the embolic protection device and the internal diameter of the lumen, then particulate matter entrained in a fluid in the lumen can bypass the protection device through the gap. It would be an advantage to be able to visualize whether or not there are any gaps between the embolic protection device and the lumenal wall. Also, when a protection device is being advanced or withdrawn from a lumen it may engage with an obstruction. The obstruction may be a stent that has been placed in a blood vessel, an area of plaque build-up, lumen tortuosity, or other structure. The operator of the embolic protection device may need to employ different techniques to advance or withdraw the device depending on the cause of engagement. Thus, it would be advantageous for the operator to be able to visualize the exact location of the device in the lumen.
Difficulties can also arise when recovering an embolic protection device. One problem that can occur is that the embolic protection device may require excessive force during recovery, for example when drawing the device into a recovery catheter. The causes of such excessive force can vary. For example, the device could be filled with embolic debris and thereby not fit into the lumen of a recovery catheter, the device may be caught on a structure such as a stent or a catheter tip, or other causes. It would be advantageous to the operator to visualize the embolic protection device so that appropriate actions can be taken so as to successfully recover the device. Further discussion of these issues is provided in U.S. Patent Publication No. 2002/0188314 A1, by Anderson et al., entitled “Radiopaque Distal Embolic Protection Device”, the contents of which are incorporated herein by reference.
The current art employs a variety of approaches to solve the problem of visualizing an embolic protection device in a patient. All of the current approaches have limitations. For example, some devices have radiopaque coatings; however coatings may become separated from the underlying substrate. Radiopaque filler materials have been employed in polymer film devices; however the fillers detract from the mechanical properties of the films and the filler/film composites, being thin, are not very visible. Strands of drawn filled tubing (DFT) have been used and have good mechanical and radiopacity characteristics; however DFT is expensive. Individual strands of radiopaque wire, such as platinum, gold, tungsten, and their alloys have good radiopacity but can have unsuitable strength or elastic yield limits, and when these strands of radiopaque wire comprise a portion of the wires in a woven structure such as a braid, these strands can alter the braid wire spacing in the vicinity of the strand of radiopaque wire due to differing mechanical properties compared to neighboring non-radiopaque wires. For some filter devices, uniform wire spacing is desired and altered braid wire spacing can cause unacceptably large pores in the braid.
Accordingly, a need exists for an embolic protection device having improved radiopacity that is inexpensive, durable, provides visibility to the appropriate regions of the device, and which uses technology that does not compromise the performance of the device.